In addition to the main purpose of degassing and impurity removal, there are many kinds of aluminum melt purification fluxes with different functions. The purification essence is to use aluminum melt purification flux to purify the melt. The difference in wettability between inclusions and melt makes inclusions spontaneously migrate from the melt into the flux, and at the same time using gas diffusion and dissolution adsorption to achieve the purpose of impurity removal and hydrogen removal.
Aluminum Melt Purification Flux can generally be divided into refining agent, covering agent, slag cleaning agent, and wall cleaning agent according to its purification mechanism.
The refining agent is based on the floating of bubbles. When it enters the aluminum melt, it decomposes under the action of high temperature or reacts with the aluminum melt to generate gas, such as HCI. The hydrogen atoms in the melt diffuse into these bubbles and are taken away, and the bubbles trap the inclusion scum during the floating process, thereby playing a role of purification. The main chemical components of refining flux are KCl, NaCl, Na3AlF6.
The density of the covering agent is smaller than that of the aluminum melt. It covers the surface of the melt, which can isolate the contact between the aluminum melt and the air, and produce a series of physical and chemical reactions with the aluminum melt, thereby preventing the aluminum melt from inhaling gas, removing hydrogen, and removing hydrogen. Miscellaneous, improve the cleanliness of the melt.
The slag remover generally has spreadability and separability, and its function is to improve the surface tension between the aluminum melt and the slag, and promote the separation of the aluminum and the slag layer. When it melts into the aluminum melt, the dissolved and adsorbed inclusions float to the surface of the aluminum solution and form a dry slag, so as to achieve the purpose of impurity removal.
The slag cleaning agent is generally composed of Na2SiF6, Na3AlF6, NaF, chloride salt, etc., among which NaCl and KCl play a covering role, because these compounds have low surface tension and low viscosity. Na3AlF6 and Na3AlF6 play a refining role, degas and remove slag, reduce the melting point of the mixed salt of NaCl and KCl, and improves the covering effect. NaF can corrode the metal melt on the Al2O32Al interface, mechanically detach the oxide film and dissolve it in the flux.
The wall cleaning agent is generally composed of exothermic substances, and its main function is to reduce the formation of oxide residues on the furnace wall or crucible wall, and prevent the mixture of flux and slag from bonding or agglomeration.
